A verdict in Tehran’s Revolutionary Court was announced on Sunday night by Gholam Hossein Mohseni Ejehi, a spokesman for the Iranian judiciary, who said on state TV that Rezaian had been found guilty, without disclosing further details about the judgement, including sentencing. In a statement, the family said Rezaian’s mother, wife and lawyer were in court on Monday to seek clarity on the verdict.

Rezaian’s family denounced the verdict on Monday as the “latest cruel step in the outrageous legal process” and promised to appeal “should the verdict be anything other than a full exoneration”. Rezaian has been jailed in Tehran for more than 14 months.

“He is an innocent man that has been kept under harsh conditions to the detriment of his health and well-being for nearly 450 days,” Rezaian’s brother Ali said in a statement. “There is worldwide condemnation for the Iranian government’s unlawful detention of Jason and calls from across the globe for his immediate release. We remain hopeful that Jason will soon be released and reunited with this family.”

Martin Baron, executive editor of the Washington Post, called the verdict an “outrageous injustice”.

“Iran has behaved unconscionably throughout this case,” Baron said in a statement. “But never more so than with this indefensible decision by a Revolutionary Court to convict an innocent journalist of serious crimes after a proceeding that unfolded in secret, with no evidence whatsoever of any wrongdoing.” For now, no sentence has been announced.

“There’s a lot more that we don’t know than we do know,” said Washington Post editor Douglas Jehl in a video for the newspaper’s website. “We don’t know what charges he’s been convicted of. We know nothing of a sentence.”

The post has said it will work with Reziaan’s lawyers to immediately appeal the case. Jehl noted in the video that the Iranian authorities have the power to overturn the conviction or pardon the journalist.

The US State Department said it is closely tracking the news coming out of Iran about Rezaian’s case but has yet to see official confirmation of his conviction.

“Regardless of whether there has been a conviction or not, we continue to call for the government of Iran to drop all charges against Jason and release him immediately,” said State Department spokesman John Kirby in a statement.

Rezaian, who holds dual Iranian and US citizenship, was arrested at his home on 22 July 2014, along with his wife, Yeganeh Salehi, also a journalist, and two friends. He was held on unspecified charges for more than seven months before appearing in court.

Freeing Jason Rezaian: a mother’s quest to bring her jailed son home from Iran.

The journalist was kept sequestered for most of his time in jail with little access to his lawyers and family. In March, he was granted access to a lawyer, though not the one of his family’s choosing. His family has said they are worried that his mental and physical health are deteriorating.

Many details remain unknown about Rezaian’s conviction. The International Campaign for Human Rights in Iran, a New York-based nonprofit, has inferred that the prosecution likely relied on “little more than a forced false ‘confession’.”

“The authorities have come up empty-handed when trying to validate their case against Rezaian,” said Hadi Ghaemi, the organization’s executive director in a statement. “So they resort to their usual tactics: force a false confession, broadcast it, and convict with impunity.”

The statement said Iranian authorities have a history of extracting confessions under duress and using them to uphold “politically motivated prosecutions”.

Frustrated with the slow pace of the trial, Ali Rezaian last month petitioned a United Nations human rights panel to help obtain his brother’s release. Ali told the Working Group on Arbitrary Detention in Geneva that Iran had violated international law – in addition to its own laws – in subjecting his brother to interrogation, solitary confinement and a closed-door trial.

Days later, Iran’s president, Hassan Rouhani, suggested that his country would consider freeing three Americans being held in its prisons, including Rezaian, in exchange for prisoners that Tehran says are being held by the US.

“If the Americans take the appropriate steps and set them free, certainly the right environment will be open and the right circumstances will be created for us to do everything within our power and our purview to bring about the swiftest freedom for the Americans held in Iran as well,” Rouhani told CNN while in New York for the UN general assembly.

Asked by reporters whether the US would consider an exchange, US secretary of state John Kerry said he had “yet to hear directly from the Iranians” on the idea.

Just weeks before Rouhani’s comments in September, Ali Larijani, the speaker of the Iranian Parliament, hinted during an interview with NPR that a prison swap between Iran and the US might be one possible way to liberate Rezaian.

The comments contrast sharply with those made by Iran’s deputy foreign minister Hassan Qashqavi, who has said that no such exchange is under consideration.

Rezaian is one of three Americans held in Iranian prisons, along with Amir Hekmati, a former US marine who was charged with espionage, and Saeed Abedini, a Christian pastor. A fourth man, Robert Levinson, disappeared in Iran in 2007 while working as a contract employee for the CIA. In July, Barack Obama said “Iran needs to help us find” Levinson.

The families of the three Americans, who are all of Iranian descent, have said they were disappointed that the nuclear deal, reached between Tehran and six world powers, did not secure their release. US officials have said they deliberately kept the nuclear negotiations separate from the release of the American prisoners in “We’re very cautiously optimistic,” Sarah Hekmati, the sister of Amir Hekmati, told the Guardian on the four-year anniversary of his detention.

State Department officials have said they repeatedly raise the issue of the captive Americans during meetings with their Iranian counterparts, with more attention paid to their cases since the deal was approved.